The Coalton Programming Language

Using Common Lisp Libraries from Coalton

Tue, 12 Aug 2025 00:00:00 +0000

We discuss how we can make an efficient, type-safe interface to existing libraries written in Common Lisp so that they can be used in Coalton code.

One of Coalton’s headline features is that it’s embedded in Common Lisp, and allows the use of Common Lisp code via the lisp operator. However, it’s not immediately obvious how one can use Common Lisp when Coalton is strongly typed. How do we do it?

Using Coalton to Implement a Quantum Compiler

Tue, 06 Sep 2022 00:00:00 +0000

By Elias Lawson-Fox, Aidan Nyquist, and Robert Smith

Updated July 1, 2025 by Robert Smith.

Introduction: Coalton and the quilc compiler

Quilc is a state-of-the-art optimizing compiler for quantum computers written in Common Lisp. It is capable of taking arbitrary quantum programs written in Quil, and compiling and optimizing them into code that conforms to the majority of quantum computing architectures that exist today.

Numbers in a Nutshell, an Update

Sat, 27 Aug 2022 00:00:00 +0000

By Robert Smith

We discuss numbers and math in Coalton, as they are so far. Coalton is under active development, so this blog post may go out of date in due time.

Introduction

Coalton is statically typed, which presents some challenges in how we work with numbers, both syntactically and semantically. For instance, consider the following Common Lisp code:

One Reason Typeclasses Are Useful

Sun, 12 Dec 2021 00:00:00 +0000

By Robert Smith

In this post, we explore one way that typeclasses are useful. We do so by first painting ourselves into a corner while building a toy Common Lisp program, and then seeing how Coalton’s typeclasses can ameliorate the issues.

A Graphics Library

Let’s write a graphics library. Or, a tad less ambitiously, let’s write some routines for performing transformations on 2D points, which might serve as the foundation of a graphics library. We’ll be interested in:

AoC 2021 Coalton Contest

Mon, 29 Nov 2021 00:00:00 +0000

By Robert Smith

Update: The prizes have been matched 1:1 by a donor who wishes to remain anonymous!

Introduction

Last September we announced Coalton, a statically typed language that is “just” another Common Lisp DSL. To our great surprise, there was a lot of excitement and fanfare, which made the development team feel quite honored and proud. It even made the top of Hacker News!

Unsurprisingly, as is the case with many open-source projects, that fanfare lead to little “conversion”; only a few people actually gave Coalton a shot and provided feedback. We are immensely thankful to those who did! The good news is that it lead to some good discussion, great PRs, and fantastic internship applications from a wonderful and diverse group of people. We won’t be able to accept everyone but I’m pleased that there’s interest in helping build out the next generation of quantum computational tools using “alien technology”. :)

Introducing Coalton: How to Have Our (Typed) Cake and (Safely) Eat It Too, in Common Lisp

Fri, 10 Sep 2021 00:00:00 +0000

By Robert Smith, Elias Lawson-Fox, Cole Scott

Updated July 1, 2025 by Robert Smith.

Introduction

Coalton is a statically typed functional programming language built with Common Lisp. We can load it like a normal Lisp library.

CL-USER> (asdf:load-system "coalton")
CL-USER> (in-package #:coalton-user)
COALTON-USER>

This is Coalton computing Fibonacci numbers by exponentiating functions (not numbers!):

(coalton-toplevel
  (declare function-power (Integer -> (:t -> :t) -> (:t -> :t)))
  (define (function-power n f)
    (if (<= n 0)
        id
        (compose f (function-power (1- n) f))))
                
  (declare fib-step ((Tuple Integer Integer) -> (Tuple Integer Integer)))
  (define (fib-step (Tuple a b))
    (Tuple b (+ a b)))
                
  (declare fib (Integer -> Integer))
  (define (fib n)
    (fst ((function-power n fib-step) (Tuple 0 1)))))

This is Coalton greeting you by making native use of Common Lisp functions:

Mon, 01 Jan 0001 00:00:00 +0000

The Coalton standard library reference.

About

Mon, 01 Jan 0001 00:00:00 +0000

Coalton is a statically typed, strictly evaluated functional programming language embedded in Common Lisp. It is an open-source project developed by the Coalton Lang developers.

Coalton developers can be reached on GitHub, via Discord, or via email at:

<this-project>@protonmail.com

where <this-project> starts with a c and ends with an n.

The Coalton Programming Language

Using Common Lisp Libraries from Coalton

Table Of Contents

Using Coalton to Implement a Quantum Compiler

Table Of Contents

Introduction: Coalton and the quilc compiler

Numbers in a Nutshell, an Update

Table Of Contents

Introduction

One Reason Typeclasses Are Useful

A Graphics Library

AoC 2021 Coalton Contest

Introduction

Introducing Coalton: How to Have Our (Typed) Cake and (Safely) Eat It Too, in Common Lisp

Introduction

About